1. Field of the Invention
The present invention is directed to a rotational vibration damper, particularly for the power train of a vehicle.
2. Background and Summary of the Invention
The rotational vibration damper of the present invention comprises a primary side and a secondary side which is rotatable with respect to the primary side around an axis of rotation against the action of a damper element arrangement, wherein the damper element arrangement comprises a first group of damper element units and a second group of damper element units, wherein for each damper element unit a first torque transmission supporting area is provided at the primary side and a second torque transmission supporting area is provided at the secondary side, and wherein the damper element units of the first group oppose a relative rotation between the primary side and the secondary side only in a first relative rotation direction, and the damper element units of the second group oppose a relative rotation between the primary side and the secondary side only in a second relative rotation direction opposed to the first relative rotation direction, wherein at least one damper element unit of the first group and at least one damper element unit of the second group are pre-loaded, and the primary side and the secondary side are pre-loaded with respect to one another in a basic relative rotation position.
FIG. 1 shows various assemblies in a hydrodynamic torque converter A which contribute to the damping of torsional vibrations or torsional nonuniformities which occur in the torque transmission state and are transmitted in a power train. A torsional vibration damper arrangement D having two radially staggered torsional vibration dampers E, E′ acting in series lies in the torque transmission path between a lockup clutch B and a driven hub C which is to be coupled with a transmission input shaft or the like so as to be fixed with respect to rotation relative to it. The torque absorbed in the engaged state of the lockup clutch B is directed to the driven hub C initially via the first torsional vibration damper E and then via the second torsional vibration damper E′ so that the torsional vibration damper arrangement D is basically considered to be an assembly which transmits the torque, or at least a portion of the torque, in the torque transmission state of the hydrodynamic torque converter A or of a power train outfitted therewith.
Another assembly contributing to the mitigation of rotational vibration is a rotational vibration damper arranged axially between the torsional vibration damper arrangement D and a turbine wheel F. This rotational vibration damper G is designed as a deflection mass pendulum arrangement whose deflection mass 26, which is located on the radially outer side and can have an annular structure or a plurality of mass elements distributed in circumferential direction, can be excited to vibrate when vibration excitations occur counter to the action of a damper element arrangement, designated in general by I. A vibration is built up in this way and is superimposed on the exciting vibrations, thereby at least partially eliminating the latter in the manner of a fixed-frequency mass damper. A rotational vibration damper constructed in this way as a deflection mass pendulum arrangement is basically to be interpreted within the meaning of the present invention as an assembly which does not conduct torque in the torque transmission state but which is coupled with the torque-transmitting assemblies. This means that the damper element arrangement I of the rotational vibration damper G does not transmit the torque that is to be transmitted in the torque transmission state between the lockup clutch B, or a housing arrangement J of the hydrodynamic torque converter A, and the driven hub C. Rather, the rotational vibration damper G in the illustrated example is coupled by a primary side K thereof, to be described more fully hereinafter, with an intermediate mass arrangement between the two torsional vibration dampers E, E′.
This primary side K of the rotational vibration damper G comprises two cover disk elements L, L′ which are arranged at a distance from one another axially and which are fixedly connected to one another, for example, by rivet bolts or the like, and are accordingly held at a distance from one another axially. The two cover disk elements L, L′ are connected to the intermediate mass arrangement, already mentioned, by a coupling member M.
A secondary side of the torsional vibration damper G comprises a central disk element N. The latter supports the deflection mass arrangement H in its radially outer area or itself contributes to the increase in the mass thereof.
The two cover disk elements L, L′ on the one hand and the central disk element N on the other hand are rotatable with respect to one another around an axis of rotation Z counter to the action of the damper element arrangement I. As is shown schematically in FIG. 2 considered from the radially outer side, the damper element arrangement I comprises a plurality of damper element units O which are, for example, arranged successively in circumferential direction around the axis of rotation Z and are preferably also situated at approximately the same radial level. For example, each damper element unit O can comprise an elastically deformable damper element P which, in the present embodiment example, is a helical compression spring. Of course, each damper element unit, or at least some of the damper element units, could comprise a plurality of damper elements P which are, for example, nested one inside the other or arranged successively in circumferential direction.
Spring windows R, R′, R″ are formed, respectively, in the cover disk elements L, L′ of the primary side K of the rotational vibration damper G and in the central disk element N of a secondary side Q of the rotational vibration damper G. Two spring windows R, R′ of cover disk elements L, L′ together define a whole spring window of the primary side K. In the state shown in FIG. 2 in which the primary side K and the secondary side Q are in a neutral relative rotation position with respect to one another, i.e., are not deflected with respect to one another by forces acting in circumferential direction, the spring windows R, R′, R″ are situated so as to substantially completely cover one another in circumferential direction, i.e., they are not offset relative to one another in circumferential direction. A damper element unit O is received in these spring windows R, R′, R″, which are respectively associated with one another, in such a way that the circumferential end areas S, S′ of this damper element unit O are supported at respective torque transmission supporting areas T, T′ of cover disk element L, torque transmission supporting areas U, U′ of cover disk element and torque transmission supporting areas W, W′ of the central disk element N, respectively, these torque transmission supporting areas adjoining the spring windows R, R′, R″ in circumferential direction.
However, this uniform support at all of these torque transmission supporting areas T, T′, U, U′, W, W′ in the neutral relative rotation position when damper element unit O is basically installed under pre-loading, exists only in hypothetical ideal cases. For reasons pertaining to manufacturing technique, it must be assumed that not all of the spring windows R, R′, R″ have the same circumferential extension, i.e., that the torque transmission supporting areas respectively formed at the latter also have exactly the same circumferential spacing. As a result, for example, in the case illustrated in FIG. 2 in which the spring window R″ in the cover disk element N has a slightly smaller circumferential extension, i.e., a slightly smaller circumferential distance between the torque transmission supporting areas W, W′ provided there, the damper element unit O or damper element P thereof contacts the torque transmission supporting areas W, W′ under pre-loading in the neutral relative rotation position, but has a slight distance from the torque transmission supporting areas T, T′, U, U′ of the cover disk elements L, L1 which corresponds to the manufacturing tolerance and which, in FIG. 2, is divided into two approximately equal partial distances a1 and a2. Accordingly, in principle there is movement play in proportion to the sum of the two partial distances a1 and a2 in which at least this damper element unit O is not effective in an area around the neutral relative rotation position and, to this extent, there is no force opposing a relative movement of the secondary side Q and, therefore, of the deflection mass arrangement H. It is only when there is a range of movement exceeding the two partial distances a1 and a2 during a greater relative deflection that the torque transmission supporting areas T, U′ of the cover disk elements L, L′, for example, come into contact with the circumferential end area S′ of the damper element unit O, while the circumferential end area S continues to remain in contact with the torque transmission supporting area W of the central disk element N. Starting from this state, a further relative rotation then takes place between the primary side K and the secondary side Q accompanied by a further compression of the damper element unit O. With relative impingement in the opposite direction, the torque transmission supporting areas 58, 62 of the cover disk elements L, L′ take effect, while torque transmission supporting area 68 of central disk element N remains effective.
This means that there is basically an undefined vibration behavior of the secondary side Q and of the deflection mass arrangement H coupled therewith in a small rotational angle area around the neutral relative rotation position because of unavoidable manufacturing tolerances. As a result, the rotational vibration damper G works with a more or less undefined spring constant of the damper element arrangement I at least in this relative rotation angle area and, therefore, its absorbing or damping action which is generally tuned to a specific frequency cannot take full effect.
A rotational vibration damper in which two opposing groups of damper element units are provided is known from WO 99/60286. Each damper element unit comprises a damper element which is constructed as a helical compression spring and which is supported in one circumferential end area at a first torque transmission supporting area of the primary side and in another circumferential end area at a second torque transmission supporting area of the secondary side. For example, two first torque transmission supporting areas of the primary side at which the damper element units of the different groups can be supported are situated between two second torque transmission supporting areas of the secondary side.
The damper element units, i.e., the helical compression springs, are installed under pre-loading so that the primary side and the secondary side are pre-loaded in a basic relative rotation position with respect to one another and, in this basic relative rotation position, the different damper element units, i.e., the helical compression springs, are not completely relaxed. In particular, the construction is effected in such a way that, in both relative rotation directions, the damper element units or helical compression springs gradually relaxing in a respective relative rotation state cannot reach a completely relaxed state over the entire range of relative rotation between the primary side and secondary side, i.e., until the maximum relative rotation between the primary side and secondary side is achieved. This results in a torsion characteristic that is constant over the entire possible relative rotation angle between the primary side and secondary side without movement play caused by manufacturing tolerances and without a change in the spring rate in the permissible range of rotational angle.
It is an object of the present invention to provide a rotational vibration damper, particularly for the power train of a vehicle, which provides an improved vibration damping behavior.
According to the invention, this object is met by a rotational vibration damper, particularly for the power train of a vehicle, comprising a primary side and a secondary side which is rotatable with respect to the primary side around an axis of rotation against the action of a damper element arrangement, wherein the damper element arrangement comprises a first group of damper element units and a second group of damper element units, wherein for each damper element unit a first torque transmission supporting area is provided at the primary side and a second torque transmission supporting area is provided at the secondary side, and wherein the damper element units of the first group oppose a relative rotation between the primary side and the secondary side only in a first relative rotation direction, and the damper element units of the second group oppose a relative rotation between the primary side and the secondary side only in a second relative rotation direction opposed to the first relative rotation direction, wherein at least one damper element unit of the first group and at least one damper element unit of the second group are pre-loaded, and the primary side and the secondary side are pre-loaded in a basic relative rotation position with respect to one another.
It is further provided that, proceeding from the basic relative rotation position of the primary side with respect to the secondary side, a pre-loading path of at least one pre-loaded damper element unit is shorter than a maximum relative rotation path of the primary side with respect to the secondary side.
While every damper element unit in the construction which was described above referring to FIGS. 1 and 2 can exhibit a restoring action regardless of the relative rotation position between the primary side and the secondary side, the damper element units of the two groups basically act in opposition to one another in the construction according to the invention. Due to the fact that the damper element units of the first group oppose a relative rotation in one direction and the damper element units of the second group oppose a relative rotation in the other, opposite direction, the primary side and the secondary side are reliably loaded in the neutral relative rotation position by these two groups. This prevents movement play between the primary side and the secondary side in the area of the neutral relative rotation position without activity of the damper element units even in the event of manufacturing tolerances which are unavoidable per se.
By providing a limited pre-loading path for at least one of the damper element units, this damper element unit acts in such a way that, starting from the neutral relative rotation position, during the relaxation of this damper element unit, it first runs through the pre-loading path in which the damper element unit relaxes to its maximum possible extent. In this phase of the relative rotation between the primary side and the secondary side, the latter rotates against the restoring action at least of an increasingly tensioned damper element unit, while the at least one gradually relaxed damper element unit basically assists this relative rotation. When the end of the pre-loading path is reached, an ongoing relative rotation continues between the primary side and the secondary side only against the action of at least one damper element unit which then continues to be increasingly tensioned, while the at least one damper element unit which is pre-loaded in the neutral relative rotation position no longer acts in an assisting manner. Accordingly, at the end of the pre-loading path a transition takes place in the restoring characteristic line of the rotational vibration damper in the sense that initially when running through the pre-loading path the characteristic line, proceeding from a value of zero, rises at a steeper inclination, which corresponds to a larger spring constant, i.e., a harder damper, and when the pre-loading path is exceeded and up until the maximum relative rotation, becomes flatter, which corresponds to a smaller spring constant and thus a reduced hardness. This transition in the characteristic line has an advantageous effect on the total vibration and damping behavior insofar as, in principle, larger vibration deflections occur at lower rotational speeds in a drive system, and the larger rotational deflections with a correspondingly softer characteristic of the rotational vibration damper are also particularly advantageous for damping or absorbing the larger vibration deflections. At higher rotational speeds, the vibration excitations in principle have a smaller vibration amplitude so that, in this state, the rotational vibration damper can operate in the range of its greater stiffness, i.e., still in the range of the pre-loading path, and therefore also provides a vibration damping behavior which is better adapted for this state of higher rotational speeds.
In this connection, it should be noted that within the meaning of the present invention the pre-loading path is that relative rotation path or relative rotation angle between the primary side and secondary side in which, proceeding from the neutral relative rotation position and, of course, in both relative rotation directions, a pre-loaded damper element unit relaxes and, in so doing, generates an action of force which assists the relative rotation in this rotating direction. This assisting action of the pre-loaded damper element unit terminates at the end of the pre-loading path so that this damper element unit essentially no longer influences the further relative rotation continuing beyond the pre-loading path until the maximum relative rotation. The maximum relative rotation of the primary side with respect to the secondary side is the maximum relative rotation angle allowed for these two groups proceeding from the neutral relative rotation position and, of course, in both relative rotation directions. For example, the maximum relative rotation can be limited by rotation stops at the primary side and secondary side, respectively, which do not permit further relative rotation.
In this regard, the construction can preferably be carried out in such a way that every damper element unit has a first supporting end area and a second supporting end area, wherein for at least one, preferably every, first supporting end area a first torque transmission supporting area is provided at the primary side and no torque transmission supporting area is provided at the secondary side, and wherein for at least one, preferably for every, second supporting end area a second torque transmission supporting area is provided at the secondary side and no torque transmission supporting area is provided at the primary side.
During relative rotation between the primary side and the secondary side in either of the two relative rotation directions, the damper element units of one of the two groups is loaded to an increased extent, while the damper element units of the other group are relieved to an increased extent or are completely relieved. In order that a defined installation position and, therefore, a defined pre-loading path can continue to be specified for the relieved damper element units, particularly also in order to prevent rattling noises, it is suggested that for at least one pre-loaded damper element unit associated with the first torque transmission supporting area of the primary side or associated with the second torque transmission supporting area of the secondary side, a relaxation limit supporting area is provided at the respective other side, primary side or secondary side, and, when a limiting relative rotation position of the primary side with respect to the secondary side is reached, which limiting relative rotation position corresponds to the pre-loading path of a pre-loaded damper element unit, the relaxation limit supporting area prevents a further relaxing of the damper element unit during relative rotation of the primary side with respect to the secondary side beyond the limiting relative rotation position.
In an alternative construction, it can be provided that at least one pre-loaded damper element unit is completely relaxed when reaching a limiting relative rotation position of the primary side with respect to the secondary side, which limiting relative rotation position corresponds to the pre-loading path.
At least one of the damper element units can comprise at least one elastically deformable damper element. This elastically deformable damper element can be constructed in a variety of ways. For example, it is possible to use elastomer material blocks such as, e.g., rubber material blocks or the like. Because of the comparatively high loading and good stability over a comparatively long operating life, at least one damper element is advantageously constructed as a spring, preferably a helical compression spring, preferably from steel material.
In order to achieve the above-mentioned action of the different groups of damper elements to the maximum extent, it is proposed that each group of damper element units comprises only pre-loaded damper element units with a limited pre-loading path. For reasons of symmetry and to prevent imbalances, it is particularly advantageous in this regard when the first group of damper element units and the second group of damper element units comprise the same number of pre-loaded damper element units with limited pre-loading path.
In this respect, it can further be provided that damper element units of the first group and damper element units of the second group are arranged successively in an alternating manner in circumferential direction.
The interaction of the damper element units of the different groups of damper element units with the primary side and secondary side, respectively, for torque transmission support and, as the case may be, also for relaxation limit support can be realized with respect to construction in a particularly simple manner in that the primary side and the secondary side have receiving windows for receiving the damper element units, and every receiving window provides a first torque transmission supporting area or a second torque transmission supporting area in at least one circumferential end area.
Since the two groups of damper element units essentially act in opposition to one another to pre-load the primary side and secondary side in direction of the relative rotation position with respect to one another, it is advantageous, particularly when the damper element units and damper elements thereof are also oriented approximately in circumferential direction, that at least one receiving window has, in its first circumferential end area, a torque transmission supporting area for a damper element unit of the first group and, in its second circumferential end area, has a torque transmission supporting area for a damper element unit of the second group.
When it is to be further provided that in a state in which the damper element units of one of the two groups are relieved, installation states which are defined for the latter are retained, for example, in an at least slightly pre-loaded state, it can be further provided that at least one receiving window has a torque transmission supporting area in its first circumferential end area and a relaxation limit supporting area in its second circumferential end area.
In principle, the construction of the torsional vibration damper can be carried out in such a way that one side, the primary side or secondary side, comprises two cover disk elements which are held at a distance from one another, and the other side, primary side or secondary side, comprises a central disk element positioned between the cover disk elements. This is a construction principle which is known, for example, from the construction of torsional vibration dampers, particularly also dual mass flywheels or the like, and which has been proven in view of the particularly stable design and the uniform loading of the damper element unit.
The principles of the present invention come into play in an advantageous manner in a rotational vibration damper particularly when the latter is constructed as a deflection mass pendulum arrangement, wherein a deflection mass arrangement is supported at one side, primary side or secondary side, and the other side, primary side or secondary side, is constructed for connecting to a torque-transmitting assembly of a power train.
Within the meaning of the present invention, a deflection mass pendulum arrangement of this kind is to be considered as an assembly which, in a torque transmitting state of a power train, is not itself integrated in the torque flow from a drive unit to a driven unit, i.e., it need not be constructed to further convey the torque to be transmitted. Rather, the rotational vibration damper is merely coupled to a torque-transmitting assembly so that it can be excited to vibrate with or by the latter and must itself merely receive or compensate for the forces generated through excitation of vibrations. This means that particularly also the damper element units of the damper element arrangement must be designed with a view to the desired absorption characteristic through generation of an oscillating pendulum movement of the deflection mass arrangement, but not with a view to the torques which also occur during very high loading in the driving state and which are to be transmitted via the power train.
The present invention is further directed to a torque transmission arrangement having a rotational vibration damper constructed according to the invention. In this respect, the torque transmission arrangement can be constructed as:
hydrodynamic torque converter,
fluid coupling,
wet clutch,
hybrid drive module.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.